Turbomachinery design typically foresees three different phases: conceptual, preliminary and detailed. Conceptual design is the first stage of industrial design process, providing mainly the architectures down-selection. Traditionally, this phase is driven by the target “performance” as the main goal to be achieved. Therefore, the design team sketches an early configuration looking at this goal. Performances can be affected by material and geometry changes, manufacturing technology and engine architecture. Conceptual design phase is dramatically important, as the outcome of the down selection will not only affect performances, but also other important parameters like ”cost” and “environmental impact”. Moreover, in conceptual phase the configuration is still under definition and the designer has the highest flexibility in defining and then designing the product. Cost and environmental sustainability are comparable to performance as drivers in industrial design process from the earliest stage. Connections between performance, cost and carbon footprint (CF) are fundamental in decision making and down-selection process. Usually, cost estimations are tailored to each design and technical requirements, to give an assessment of the costs from the buyer’s point of view. Assessment of the environmental impacts can be carried out by means of the Life Cycle Assessment (LCA) methodology (ISO 14040: 2006, ISO 14044:2006), looking at the whole life cycle of the product. Therefore, as boundary definition can be different, there is a possibility that cost estimation and LCA results are not consistent with each other due to different system boundaries, leading to misinformed decisions. To overcome this issue, the principles underlying the environmental Life Cycle Costing (e-LCC) method can be used (Hunkeler et al. 2008). It integrates both LCA and LCC studies, based on the same functional unit and system boundaries.

This article will present a case study of a supercritical CO2 turboexpander inner casings’ subsystem conceptual design and architecture down selection to propose an approach for maximizing product’s sustainability and performance. Results show the relevance of the geographical location of suppliers on the CF, as well as how small changes on the overstock materials could lead to a relevant change in costs.

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